This invention relates generally to document handling devices, and more particularly, to an arrangement for adaptively driving a flag element of a document handling device.
Document-handling devices are commonly used today to quickly move and sort a variety of documents, such documents generally consisting of one or more individual sheets. A feeding mechanism is used to introduce each sheet to the document transport for processing and sorting, and each sheet is often automatically fed from a document stack via this feeding mechanism. It will be appreciated that it is important to introduce each sheet individually, using consistent spacing between each sheet, in order to permit the fastest feed rate possible while still maintaining proper document processing.
In high-speed document sorters, a hopper is often used to locate and support a stack of sheets and supply them to the feeding mechanism, while a device, commonly known as a flag, is used to move the stack of sheets across the hopper during feeding. In order to create this movement, the flag must apply a force to the last sheet in the stack.
A number of systems are commonly known for applying this flag force. One such flag driving system is a non-variable dead weight system. This system uses potential energy derived from a constant weight that is attached to the flag by a cord or some other flexible connector. The constant weight creates a tension on the cord, and therefore, a force on the flag. The net result is a constant force transmitted from the flag onto the document stack.
A drawback of this non-variable dead weight system is that it is not possible to optimize the performance of the document-handling device. More specifically, it is improbable, if not impossible, to maintain proper document or sheet spacing through such arrangement. It will be appreciated that this results from the inability to variably control the force exerted by the flag on the document stack. For example, pushing a stack of several thousand sheets requires for more force than pushing the last few sheets. The constant uncontrollable nature of the force exerted on the document stack, will thus often result in wider spacing where there are many sheets, and closer spacing where there are fewer. This, in turn, results in poor document-handling device performance.
Another method of producing flag force against a document stack is to use some sort of motor arrangement with an associated electronic control system, to optimally control the flag force. To best adapt to flag force requirements, many motor driven flag systems often use sensors to measure and adjust the flag motion and force. However, because the mechanical environment created by a feed sorter can be turbulent, the sensors must undergo filtering to ensure that their sensed values are accurate. Thus, although these systems are generally more responsive to flag force requirements, they are generally complex, costly and subject to high maintenance.
In U.S. patent application Ser. No. 09/521,162 (Spall), an arrangement for driving the flag element of a document-handling device was disclosed, such arrangement including a constant weight 80 and cam 82 having variably increasing radii 84a and 84b, wherein 84a is a minimal radius and 84b is a maximum radius (FIG. 1). Although this arrangement was found to operate adequately under normal service conditions, even under cam motor 86 failure, certain anomalous conditions were found to render the device unserviceable. More specifically, it was found in those instances where interruption in power to cam motor 86, or failure of cam motor 86 itself, occurred while flag 88 was in the extreme left of the hopper 90, and thus cam 82 was rotated to its extreme clockwise position, attempted repair of the situation caused further problems. In this situation, the document-handling device operator might move the flag 88 to the right. In such instance, the constant weight 92 would be drawn upwards, the cam 82 would rotate counter-clockwise about shaft 94, and a portion of flag string 96 would be unwound from the cam 82. Should the operator then release flag 88, it will move back towards the left under the action of constant weight 80. However, since there is no driving torque on the cam 82, it will not move, and the extended portion of flag string 96 will not be drawn back in to wrap around cam 82, as would be the case were the cam motor 86 energized or otherwise operating correctly. As a result, the extended portion of the flag string 96 falls away from the cam 82, often necessitating a service intervention to replace the flag string 96 on the cam 82 in order to restore correct operation of the document-handling device.
It is therefore desirable to provide a document-handling apparatus with an improved mechanism that produces a flag force that is directly responsive to the force needed to move the document stack, and which is substantially immune to, or self-correcting of, anticipated operator repair attempts that might disable the previously disclosed system.
It is therefore an object of the present invention to provide an improved feeding mechanism for a document-handling device.
It is another object of the invention to provide a device n improved feeding mechanism that produces a flag force that is directly responsive to the force needed to move the document stack.
It is yet another object of the invention to provide an improved feeding mechanism for driving a flag element in a manner so as to present an adjustable force for moving a document stack.
A further object of the present invention is to provide an arrangement for adaptively driving the flag element of a document-handling device.
Accordingly, the present invention is directed to an arrangement for adaptively driving a flag element against a document stack of a document-handling device. In a preferred embodiment of the present invention, a first cam is connected to a flag element, and is rotationally mounted on the shaft of a motor that provides a constant torque. The rotation of the first cam exerts a first force on the flag element. The first cam is shaped such that the first force exerted on the flag element varies in accordance with the number of sheets in the document stack of the document-handling device. In another embodiment of the present invention, a second cam is rotatably connected to the first cam, the second cam having a fixed weight acting upon it tangentially by means of a cord or similar flexible connection. The rotation of the second cam produces a second, additive torque upon the first cam and thus a second additive force upon the flag. The two cams are shaped, and mounted with an angular relationship such that the torque applied by the second cam (due to the constant weight), when transmitted through the first cam, results in a constant additive force upon the flag.